This invention relates generally to setback thermostats and, more particularly, to a method and apparatus for balancing load management by the use of both primary and auxiliary setback mechanisms.
In an effort to reduce peak load requirements during extreme temperature conditions, utility companies have instituted utility load management programs whereby a user may be offered reduced rates if the user is willing to “setback” their thermostats during such period of high energy use. This process occurs automatically by the utility communicating directly with the users thermostats, and also includes provisions for the user to override such a setback condition if he so desires. Unless the user is overriding the system, the time periods in which the user's thermostat is “setback”, is therefore based only on the demand to the utility.
In addition to the procedure of setting back the thermostat for HVAC (i.e. heating, ventilating and air conditioning) systems, provision is also made for setback of energy that is provided to run non-HVAC, auxiliary devices such as pool pumps, pool heaters, hot water heaters, hot tubs and the like. These devices do not have thermostats and may or may not have temperature sensors. Accordingly, the common approach for setback in these devices is on a duty cycle basis. For example, a 50% duty cycle may be imposed whereby the device is alternately turned off and turned on for equal periods of time with the effect that over the entire period, the device is only on half the time.
From the above description it will be recognized that, since there is no coordination between the setback times for HVAC systems and for the auxiliary devices, there will be periods when neither the HVAC nor the auxiliary devices are in a setback condition. There will also be times when both the HVAC systems and the auxiliary devices are in a setback mode. The result is that the total time in which the various systems are in a setback condition is very non-uniform, thereby resulting in a less uniform demand to the utility. This condition is undesirable for the utility since its overall demand will be non-uniform for the same reasons.